Give Daniel Radcliffe plenty of credit—he's certainly pushing himself as far beyond Harry Potter as humanly possible. Last year, the 24-year-old actor took his first steps toward thespian adulthood with The Woman in Black, a slick piece of old-school Gothic horror in which he combatted supernatural forces and the death of his character's wife. Here in Toronto, Radcliffe's premiering three new, decidedly grown-up films, two of which aren't genre fare: Kill Your Darlings, with Radcliffe boldly going man-on-man as beat poet Allen Ginsberg, and The F Word, a rom-com opposite indie darling Zoe Kazan.

The oddest and most intriguing of Radcliffe's TIFF projects, however, is Horns, an adaptation of novelist Joe Hill's (yes, the son of Stephen King) excellent 2010 novel. A hybrid of dark fantasy and murder mystery, Hill's book is a singular work. Tonally, it's a tightrope that Hill navigates brilliantly, seamlessly shifting from darkness to heartwarming moments, comedic beats that flow naturally, and fantastical weirdness. Which is to say, it's a screenwriter's worst job come true. As it turns out, that book-to-film difficulty is exemplified in Horns the film. Directed by horror veteran Alexandre Aja (High Tension, Piranha 3D), it's an ambitious and earnestly made misfire, dragged down by its own schizophrenia.

Fans of Hill's novel will be pleased to hear that, for the most part, Aja and screenwriter Keith Bunin remain faithful to their source material, though the areas where they tweak are sadly calamitous. The gonzo story's the same: Ig Perrish (Radcliffe), grieving over the unsolved murder of his lifelong girlfriend, Merrin (Juno Temple, as hauntingly enchanting as ever), is the primary suspect as far as his community's concerned. Labeled a murderer, and even a "devil" in the local newspaper, Ig's boozing hard and floating through life in mourning, until, after one very hard night of drinking alongside Merrin's death site, he wakes up with two horns growing out of his temples. And whenever he's next to someone, for some inexplicable reason, the horns make them tell Ig exactly what they're feeling, no filter; he's also able to see a person's darkest secrets play out in flashbacks whenever he touches them. Which, as you might have guessed, works out well while you're playing makeshift detective in order to figure out who killed your girl.

In its earliest stages, Horns is a far-out delight, with Aja and Bunin mining laughs from Ig's sudden ability to hear the truth from folks. At the doctor's office, for instance, a mother opens up to him about how she'd love to drop-kick her little, crying machine of a daughter; elsewhere, a drunken jump off, Glenna (Kelli Garner) acknowledges her town-bicycle status, says she's worthless, and starts stuffing her face in a box of donuts. It's in these scenes that Horns works well a dark comedy. But Aja also wants high-powered emotional developments and frequent bursts of gruesome violence to register just as effectively, which isn't the case. Horns bounces around from one tone to the next so rapidly that it's tough to figure out just what kind of movie the filmmakers hoped to deliver. One second, Ig's having a fiery heart-to-heart with older brother (Joe Anderson), and the next he's watching two beat cops admit their homosexual urges to one another, and while you're still trying to decipher the film's aim, snakes show up and chow down on someone.

In Hill's book, the various moods congeal are joined by the crisp, eloquent prose, which delves into all of the main characters' psyches enough to make it easy for the reader to play along with whatever bizarre things are afoot. Aja's film, though, is too invested in Ig's reactions to his nightmarish predicament to allow any of its supporting character—particularly one who's prominent in Hill's novel but whose role gets minimized here, to the film's detriment (though we'll leave it at that, lest there be spoilers)—to help ground the out-there plot. As a result, it's Radcliffe's show, yet he seems similarly confused as to what kind of movie he's acting in. When he's not overselling Ig's more manic actions, Radcliffe nails the quieter parts—his chemistry with Temple, seen in flashbacks, is wonderful. He's pitch-perfect as Regular Ig and awkwardly over-compensational when, um, horny.

Aja, on the other hand, exhibits more confidence during the film's crazier sequences, where he's able to tap into the impeccable sense of tension and visceral impact he nailed in High Tension and his underrated 2006 remake of The Hills Have Eyes. Clearly an attempt to sidestep away from all-out horror for a change, Horns shows Aja simultaneously growing as a director and still figuring himself out. Late into the film, one character is forcefully persuaded to consume a ridiculous amount of narcotics, leading to a drug trip where Aja achieves a WTF highpoint that's like equal parts Tim & Eric and Rob Zombie's The Lords of Salem. He might have hoped that Horns would prove he's more than a horror champ, but scenes like that remain Aja's bread and butter.

Horns represents a major career turning point for both Radcliffe and Aja, and, for that, it's worthy of some admiration—most actors coming off of record-breaking Hollywood franchises and horror directors known for strong remakes would scoff at such wildly challenging material. That respectful leniency only goes so far, though. Despite their best efforts, Horns' actor/director tandem were in over their head with Hill's novel. If only Ig had been on set to get someone to candidly let them know that.